1. Field of the Invention
The present invention relates to a method for manufacturing hybrid integrated circuits (ICS) and, more particularly, to a method for mounting parts on hybrid integrated circuit boards.
2. Description of the Related Art
After a plurality of circuits such as ICs have been formed on a surface of a silicon wafer by a semiconductor manufacturing process which includes a sequence of process steps such as patterning, ion implantation diffusion, and testing, it has been customary to separate the silicon wafer into individual IC chips in the following manner. As shown in FIG. 1, an adhesive sheet 106 is first applied to the reverse surface 104b of a silicon wafer 104 on which no circuit is formed. The adhesive sheet 106, which is a thin film made of a plastic and coated with an adhesive material, easily undergoes plastic deformation from the application of tensile force. Then, as shown in FIG. 2, grooves 105 for wafer separation are formed along the boundaries between adjacent ICs on the silicon wafer 104 by means of a dicing saw (not shown), the grooves 105 extending from an obverse surface 104a, on which circuits are formed, toward the reverse surface 104b. Each of the grooves 105 is formed to a depth which reaches approximately the mid position of the silicon wafer 104 as viewed in the direction of the thickness thereof.
In addition, as shown in FIG. 1, an elastic sheet 102 having elasticity is carried on a fixed stage 101 made of metal such as stainless steel, and a filter paper 103 is carried on the sheet 102 to protect the obverse surface 104a of the silicon wafer 104. Then, the silicon wafer 104 is carried on the filter paper 103 with the adhesive sheet 106 applied thereto with the surface 104a in contact with the filter paper 103. An aluminum foil 107 having a thickness of some tens of microns is carried on the adhesive sheet 106. In this state, a roller 108 made of stainless steel is rolled over the aluminum foil 107 to apply a downward pressure to the silicon wafer 104. As the roller 108 travels, deformation occurs in the corresponding portion of the sheet 102, and thus the corresponding portion of the silicon wafer 104 is deformed. As a result of the deformation, stresses are concentrated upon the bottom portion of the corresponding groove 105 formed in the silicon wafer 104. Thus, cleavage occurs in the portion of the silicon wafer 104 which extends from the bottom of the groove 105 in the direction of the thickness of the silicon wafer 104, and the adjacent ICs are separated along the cleaved surfaces. In this fashion, as the roller 108 rolls, the silicon wafer is sequentially separated into individual ICs.
Subsequently, the spaces between the adjacent ICs are expanded by applying a tensile force to the adhesive sheet 106, stretching it, and causing plastic deformation of it. Furthermore, the individual ICs are removed from the adhesive sheet 106 and mounted on a circuit board, a lead frame or the like.
However, if the above-described conventional method for separating a silicon wafer is applied to hybrid integrated circuits, the following problems will occur since it is necessary to mount component parts on such a hybrid integrated circuit board. More specifically, if a component part is to be mounted on each separated portion of the circuit board, it is necessary to mount or position each circuit board in place and, hence, the step of mounting parts becomes complicated, thus resulting in an increase in cost. Furthermore, since each separated portion is too small to be easily handled, it is difficult to automate the process for manufacturing hybrid integrated circuits. In contrast, if component parts are mounted prior to wafer separation and the wafer is then separated into individual chips, the following problems occur. When pressure is applied to the board, stresses are applied to the connections of the component parts or the component parts themselves and the reliability of the obtained hybrid integrated circuits may thereby deteriorate. In addition, since various parts are carried on the boards, it is still difficult to automate the process for manufacturing hybrid integrated circuits.